The present invention relates to surgical screws, and, in particular, to means for preventing counter-rotation of a surgical screw during the period that it remains in its installed position within the patient.
Surgical screws used in the fixation of bone fractures and separations occurring in a patient are well-known in the art. One representative example of a surgical screw used in the fixation of hip fractures is disclosed in U.S. Pat. No. 2,570,465. This prior art surgical screw has a generally flat head with a smooth, frusto-conical under surface, a smooth, cylindrical shank, and a helically threaded distal end portion. The screw is installed through a pre-drilled bore extending from the femur through the center of the hip fracture in the femoral neck and into the center of the ball-shaped head seated within a socket in the pelvic bone. The screw may include an axial bore extending completely through the center of the screw for receiving a long guide pin used to axially align the screw prior to its installation. An additional surgical screw for the fixation of fractures of the femoral neck is disclosed in U.S. Pat. No. 4,383,527. ther surgical screws known in the art include the Mecron and the Howse cannulated screws.
The surgical screw of the present invention differs from the above-mentioned surgical screws in that its principal use is for the internal fixation of an acromio-clavicular separation. The improved screw is installed to maintain the clavicle in a fixed position with respect to the coracoid once the separation has been reduced. To prevent counter-rotation of the screw while in place within the patient, one or more inclined holes or bores are provided through the head of the screw. A long, slender locking pin is inserted into and through an appropriate one of the inclined holes into a small pre-drilled hole within the clavicle; the axis of the hole in the head of the screw being inclined with respect to the longitudinal axis of the screw, enabling the long, slender locking pin to be staked into the clavicle to prevent counter-rotation of the screw. Any counter-rotation or loosening of the screw, once installed, seriously jeopardizes the reduction of the separation and a prompt recovery.
Accordingly, the principal object of the present invention is to provide a surgical screw which can be retained in its installed position without the risk of counter-rotation during the period that the screw must remain in place within the patient.
The above object of and the brief introduction to the present invention will be more fully understood, and further objects and advantages will become apparent, from a study of the following detailed description in connedtion with the drawings.